The cross-pathway control system regulates production of the secondary metabolite toxin, sirodesmin PL, in the ascomycete, Leptosphaeria maculans.

Background: Sirodesmin PL is a secondary metabolite toxin made by the ascomycetous plant pathogen, Leptosphaeria maculans. The sirodesmin biosynthetic genes are clustered in the genome. The key genes are a non-ribosomal peptide synthetase, sirP, and a pathway-specific transcription factor, sirZ.

Plant homologs of the Plasmodium falciparum chloroquine-resistance transporter, PfCRT, are required for glutathione homeostasis and stress responses.

In Arabidopsis thaliana, biosynthesis of the essential thiol antioxidant, glutathione (GSH), is plastid-regulated, but many GSH functions, including heavy metal detoxification and plant defense activation, depend on cytosolic GSH. This finding suggests that plastid and cytosol thiol pools are closely integrated and we show that in Arabidopsis this integration requires a family of three plastid thiol transporters homologous to the Plasmodium falciparum chloroquine-resistance transporter, PfCRT. Arabidopsis mutants lacking these transporters are heavy metal-sensitive, GSH-deficient, and hypersensitive to Phytophthora infection, confirming a direct requirement for correct GSH homeostasis in defense responses.

Metal binding affinities of Arabidopsis zinc and copper transporters: selectivities match the relative, but not the absolute, affinities of their amino-terminal domains.

HMA2, HMA4, and HMA7 are three of the eight heavy metal transporting P(1B)-type ATPases in the simple plant Arabidopsis thaliana. The first two transport Zn(2+), and the third transports Cu(+). Each protein contains soluble N-terminal metal-binding domains (MBDs) that are essential for metal transport.

Functional analysis of the heavy metal binding domains of the Zn/Cd-transporting ATPase, HMA2, in Arabidopsis thaliana.

The Zn/Cd-transporting ATPase, HMA2, has N- and C-terminal domains that can bind Zn ions with high affinity. Mutant derivatives were generated to determine the significance of these domains to HMA2 function in planta. Mutant derivatives, with and without a C-terminal GFP tag, were expressed from the HMA2 promoter in transgenic hma2,hma4, Zn-deficient, plants to test for functionality.

The use of the zinc-fluorophore, Zinpyr-1, in the study of zinc homeostasis in Arabidopsis roots.

* The usefulness of the zinc (Zn)-fluorophore, Zinpyr-1, to examine the localization of Zn in the roots of Arabidopsis has been investigated. * In wild-type roots Zinpyr-1 fluorescence was predominantly in the xylem. The fluorescence signal was abolished by the application of the Zn-chelator, N,N,N',N-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and was increased by increasing exogenous Zn in the medium, indicating that fluorescence reflected relative Zn concentrations.

The ABC transporter gene in the sirodesmin biosynthetic gene cluster of Leptosphaeria maculans is not essential for sirodesmin production but facilitates self-protection.

Epipolythiodioxopiperazine toxins are secreted by a range of fungi, including Leptosphaeria maculans, which produces sirodesmin, and Aspergillus fumigatus, which produces gliotoxin. The L. maculans biosynthetic gene cluster for sirodesmin includes an ABC transporter gene, sirA.